Algal elongase 6

ABSTRACT

Provided herein are exemplary isolated nucleotide sequences encoding polypeptides having elongase activity, which utilize fatty acids as substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/459,215, filed Apr. 12, 2012, now U.S. Pat. No. 8,809,046,which claims the benefit and priority of U.S. Patent ProvisionalApplication Ser. No. 61/480,364 filed Apr. 28, 2011, titled “Elongases,”which is hereby incorporated by reference.

The present application is related to U.S. Non-Provisional patentapplication Ser. No. 12/581,812 filed on Oct. 19, 2009, titled“Homologous Recombination in an Algal Nuclear Genome,” which is herebyincorporated by reference.

The present application is related to U.S. Non-Provisional patentapplication Ser. No. 12/480,635 filed on Jun. 8, 2009, titled “VCP-BasedVectors for Algal Cell Transformation,” which is hereby incorporated byreference.

The present application is related to U.S. Non-Provisional patentapplication Ser. No. 12/480,611 filed on Jun. 8, 2009, titled“Transformation of Algal Cells,” which is hereby incorporated byreference.

REFERENCE TO SEQUENCE LISTINGS

The present application is filed with sequence listing(s) attachedhereto and incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to molecular biology, and more specifically, toalgal elongases.

SUMMARY OF THE INVENTION

Isolated nucleotide sequences encoding polypeptides having elongaseactivity, which utilize fatty acids as substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the nucleotide sequence encoding elongase 1 (SEQ IDNO:1).

FIG. 2 illustrates the nucleotide sequence encoding elongase 2 (SEQ IDNO:2).

FIG. 3 illustrates the nucleotide sequence encoding elongase 3 (SEQ IDNO:3).

FIG. 4 illustrates the nucleotide sequence encoding elongase 4 (SEQ IDNO:4).

FIG. 5 illustrates the nucleotide sequence encoding elongase 5 (SEQ IDNO:5).

FIG. 6 illustrates the nucleotide sequence encoding elongase 6 (SEQ IDNO:6).

FIG. 7 illustrates the nucleotide sequence encoding elongase 7 (SEQ IDNO:7).

FIG. 8 illustrates the nucleotide sequence encoding elongase 8 (SEQ IDNO:8).

FIG. 9 illustrates the amino acid sequence encoding elongase 1 (SEQ IDNO:9).

FIG. 10 illustrates the amino acid sequence encoding elongase 2 (SEQ IDNO:10).

FIG. 11 illustrates the amino acid sequence encoding elongase 3 (SEQ IDNO:11).

FIG. 12 illustrates the amino acid sequence encoded by elongase 4 (SEQID NO:12).

FIG. 13 illustrates the amino acid sequence encoded by elongase 5 (SEQID NO:13).

FIG. 14 illustrates the amino acid sequence encoded by elongase 6 (SEQID NO:14).

FIG. 15 illustrates the amino acid sequence encoded by elongase 7 (SEQID NO:15).

FIG. 16 illustrates the amino acid sequence encoded by elongase 8 (SEQID NO:16).

DETAILED DESCRIPTION OF THE INVENTION

A fatty acid is a carboxylic acid with a long aliphatic tail (chain),which is either saturated or unsaturated. Saturated fatty acids arelong-chain carboxylic acids that usually have between 12 and 24 carbonatoms and have no double bonds. Unsaturated fatty acids have one or moredouble bonds between carbon atoms. Most naturally occurring fatty acidshave a chain of an even number of carbon atoms, from 4 to 28. Elongasesare enzymes which lengthen fatty acids by adding two carbon atoms to afatty acid's carboxylic acid end.

Provided herein are isolated nucleotide sequences encoding polypeptideshaving elongase activity, which utilize fatty acids as substrates.

The inventors sequenced the entire genome of algal genus Nannochloropsisand identified genes involved in fatty acid metabolism. They identifiedvarious elongases, including exemplary elongases which they designatedas elongases 1-9.

The inventors manipulated the activities of the above-specifiedexemplary elongase genes by:

1. Overexpression of the subject elongase gene with a strong promoter.

2. Promoter replacement or promoter insertion in front of the subjectelongase gene within the genome via homologous recombination.

3. Knock out of the subject elongase gene via insertion of atransformation construct into the gene or replacement of a part of orthe entire subject elongase gene via homologous recombination.

Exemplary support for the above-mentioned methods may be found in U.S.Non-Provisional patent application Ser. No. 12/581,812 filed on Oct. 19,2009, titled “Homologous Recombination in an Algal Nuclear Genome,” U.S.Non-Provisional patent application Ser. No. 12/480,635 filed on Jun. 8,2009, titled “VCP-Based Vectors for Algal Cell Transformation,” and U.S.Non-Provisional patent application Ser. No. 12/480,611 filed on Jun. 8,2009, titled “Transformation of Algal Cells,” all of which are herebyincorporated by reference.

Accordingly, the inventors were able to manipulate the activities of thevarious exemplary elongases for the purpose of modifying the contents ofcertain fatty acids within algal genus Nannochloropsis.

Some of these elongases, i.e. Elongases 6-8, are down-regulated underconditions when poly unsaturated fatty acid (“PUFA”) biosynthesis isdown-regulated as well (i.e. during Nitrogen starvation). These genesare excellent targets for over-expression, in order to achieve elevatedPUFA biosynthesis. Down-regulation of these (or other) genes, as anexample, by replacement of the endogenous promoter or insertion of aweaker promoter in front of the respective elongase gene could lead to ahigher content of short chain fatty acids. Down-regulation oftranscription could also be achieved, in some cases, by insertion of acommonly strong promoter in front of the respective elongase gene,presumably by modifying the respective chromatin arrangement around thesaid elongase gene, thus leading to a lower transcription level. Also,the introduction of point mutations into the gene when inserting anotherpromoter in front of such a gene via the homologous recombination flanksutilized, could lead to an altered activity of the respective geneproducts.

Over expression and knock out mutants of said elongase genes suggestthat at least 4 elongases with overlapping functions are operating inthe biosynthesis pathway leading to Eicosapentaenoic acid (“EPA”): theseare, but not limited to: Elongases 5, 6, 7, and 9. Transcriptomeanalysis also suggests that Elongase 8 is operating as well in the fattyacid biosynthesis pathway to EPA.

FIG. 1 illustrates the nucleotide sequence encoding elongase 1 (SEQ IDNO:1).

FIG. 2 illustrates the nucleotide sequence encoding elongase 2 (SEQ IDNO:2).

FIG. 3 illustrates the nucleotide sequence encoding elongase 3 (SEQ IDNO:3).

FIG. 4 illustrates the nucleotide sequence encoding elongase 4 (SEQ IDNO:4).

FIG. 5 illustrates the nucleotide sequence encoding elongase 5 (SEQ IDNO:5).

FIG. 6 illustrates the nucleotide sequence encoding elongase 6 (SEQ IDNO:6).

FIG. 7 illustrates the nucleotide sequence encoding elongase 7 (SEQ IDNO:7).

FIG. 8 illustrates the nucleotide sequence encoding elongase 8 (SEQ IDNO:8).

FIG. 9 illustrates the amino acid sequence encoding elongase 1 (SEQ IDNO:9).

FIG. 10 illustrates the amino acid sequence encoding elongase 2 (SEQ IDNO:10).

FIG. 11 illustrates the amino acid sequence encoding elongase 3 (SEQ IDNO:11).

FIG. 12 illustrates the amino acid sequence encoded by elongase 4 (SEQID NO:12).

FIG. 13 illustrates the amino acid sequence encoded by elongase 5 (SEQID NO:13).

FIG. 14 illustrates the amino acid sequence encoded by elongase 6 (SEQID NO:14).

FIG. 15 illustrates the amino acid sequence encoded by elongase 7 (SEQID NO:15).

FIG. 16 illustrates the amino acid sequence encoded by elongase 8 (SEQID NO:16).

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments.

What is claimed is:
 1. A method of modulating poly unsaturated fattyacid biosynthesis in an algal cell, said method comprising: enhancing orsuppressing expression of an elongase 6 comprising the amino acidsequence of SEQ ID NO: 14 in said algal cell, wherein said enhancingexpression comprises replacement of an endogenous promoter with a strongpromoter in front of a gene encoding said elongase 6, wherein saidsuppressing expression is selected from the group consisting ofreplacement of an endogenous promoter with a weak promoter in front of agene encoding said elongase 6, an insertion in a gene encoding saidelongase 6 comprising the amino acid sequence of SEQ ID NO: 14, and adeletion or a substitution of a portion or a full length of said geneencoding elongase 6 comprising the amino acid sequence of SEQ ID NO: 14,wherein said strong promoter is stronger than said endogenous promoterand said weak promoter is weaker than said endogenous promoter; therebymodulating poly unsaturated fatty acid biosynthesis in said algal cell.2. The method of claim 1, wherein said expression of said elongase 6 isenhanced and eicosapentaenoic acid (EPA) production is increased in saidalgal cell relative to an algal cell without said enhanced expression.3. The method of claim 1, wherein said expression of said elongase 6 issuppressed and EPA production is decreased in said algal cell relativeto an algal cell without said suppressed expression.
 4. The method ofclaim 1, wherein said algal cell is a Nannochloropsis cell.
 5. Themethod of claim 1, wherein said algal cell comprises an insertion insaid gene encoding said elongase 6 comprising the amino acid sequence ofSEQ ID NO:
 14. 6. The method of claim 1, wherein said algal cellcomprises a deletion or a substitution of a portion or a full length ofsaid gene encoding elongase 6 comprising the amino acid sequence of SEQID NO: 14.